"ADR no longer available"...UGH!!!

I have been searching, in vain, for the past several weeks for a certain ADR. A few times it has popped up on the Disney dining booking site and when I hit "reserve", it then says "this is no longer available"! When it's happened, I've gotten so excited to finally see the ADR I need only to be let down a few seconds later.

I wouldn't give up but no that has never happened to me. I've switched a lot in the past week since things I now want have become available but if I finally see it available, no it does not go away when I click reserve.